package class03;

import com.sun.xml.internal.ws.api.ha.HaInfo;

/**
 * @author zhangchaoliang
 * create 2022
 */
public class MergeSort2 {
   public static void mergeSort1(int[] arr){
       if (arr==null||arr.length<2)
           return;
       process(arr,0,arr.length-1);
   }

   public static void process(int[] arr,int L,int R){
       if (L==R)
           return;
       int mid = L+((R-L)>>1);
       process(arr,L,mid);
       process(arr,mid+1,R);
       merge(arr,L,mid,R);
   }

   public static void merge(int[] arr,int L,int M,int R){
       int[] help = new int[R-L+1];
       int i=0;
       int p1=L;
       int p2=M+1;

       while (p1<=M&&p2<=R)
           help[i++]=arr[p1]<=arr[p2]?arr[p1++]:arr[p2++];
       while (p1<=M)
           help[i++]=arr[p1++];
       while (p2<=R)
           help[i++]=arr[p2++];
       for (i=0;i<help.length;i++)
           arr[L+i]=help[i];

   }

   public static void mergeSort2(int[] arr){
       if (arr==null||arr.length<2)
           return;
       int N = arr.length;
       int mergeSize = 1;
       while (mergeSize<N){
           int L =0;
           while (L<N){
               int M = L+mergeSize-1;
               if (M>=N)
                   break;
               int R =Math.min(M+mergeSize,N-1);
               merge(arr,L,M,R);
               L = R+1;
           }
           if (mergeSize>N/2)
               break;
           mergeSize<<=1;
       }
   }

    // for test
    public static int[] generateRandomArray(int maxSize, int maxValue) {
        int[] arr = new int[(int) ((maxSize + 1) * Math.random())];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
        }
        return arr;
    }

    // for test
    public static int[] copyArray(int[] arr) {
        if (arr == null) {
            return null;
        }
        int[] res = new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            res[i] = arr[i];
        }
        return res;
    }

    // for test
    public static boolean isEqual(int[] arr1, int[] arr2) {
        if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) {
            return false;
        }
        if (arr1 == null && arr2 == null) {
            return true;
        }
        if (arr1.length != arr2.length) {
            return false;
        }
        for (int i = 0; i < arr1.length; i++) {
            if (arr1[i] != arr2[i]) {
                return false;
            }
        }
        return true;
    }

    // for test
    public static void printArray(int[] arr) {
        if (arr == null) {
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }
        System.out.println();
    }

    // for test
    public static void main(String[] args) {
        int testTime = 500000;
        int maxSize = 100;
        int maxValue = 100;
        System.out.println("测试开始");
        for (int i = 0; i < testTime; i++) {
            int[] arr1 = generateRandomArray(maxSize, maxValue);
            int[] arr2 = copyArray(arr1);
            mergeSort1(arr1);
            mergeSort2(arr2);
            if (!isEqual(arr1, arr2)) {
                System.out.println("出错了！");
                printArray(arr1);
                printArray(arr2);
                break;
            }
        }
        System.out.println("测试结束");
    }
}
